Page 40 - The Mechatronics Handbook

FIGURE 2.10 Real-time simulation: hybrid structures. (a) Hardware-in-the-loop simulation. (b) Control prototyping.

and the sensors are simulated. The reason is that actuators and the control hardware very often form
one integrated subsystem or that actuators are difficult to model precisely and to simulate in real time.
(The use of real sensors together with a simulated process may require considerable realization efforts,
because the physical sensor input does not exist and must be generated artificially.) In order to change
or redesign some functions of the control hardware or software, a bypass unit can be connected to the
basic control hardware. Hence, hardware-in-the-loop simulators may also contain partially simulated
(emulated) control functions.
The advantages of the hardware-in-the-loop simulation are generally:
• design and testing of the control hardware and software without operating a real process (“moving
the process field into the laboratory”);
• testing of the control hardware and software under extreme environmental conditions in the
laboratory (e.g., high/low temperature, high accelerations and mechanical shocks, aggressive
media, electro-magnetic compatibility);
• testing of the effects of faults and failures of actuators, sensors, and computers on the overall system;
• operating and testing of extreme and dangerous operating conditions;
• reproducible experiments, frequently repeatable;
• easy operation with different man-machine interfaces (cockpit-design and training of operators);
and
• saving of cost and development time.

Control Prototyping
For the design and testing of complex control systems and their algorithms under real-time constraints,
a real-time controller simulation (emulation) with hardware (e.g., off-the-shelf signal processor) other
than the final series production hardware (e.g., special ASICS) may be performed. The process, the
actuators, and sensors can then be real. This is called control prototyping (Fig. 2.10(b)). However, parts
of the process or actuators may be simulated, resulting in a mixture of HIL-simulation and control
prototyping. The advantages are mainly:
• early development of signal processing methods, process models, and control system structure,
including algorithms with high level software and high performance off-the-shelf hardware;
• testing of signal processing and control systems, together with other design of actuators, process
parts, and sensor technology, in order to create synergetic effects;

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